Tumour vascularity is of prognostic significance in adult, but not paediatric astrocytomas

Implications of Cellular Immaturity in Necrosis and Microvascularization in Glioblastomas IDH-Wild-Type

Necrosis and increased microvascular density in glioblastoma IDH-wild-type are the consequence of both hypoxia and cellular immaturity. Our study aimed to identify the main clinical-imaging and morphogenetic risk factors associated with tumor necrosis and microvascular in the prognosis of patient survival. We performed a retrospective study (10 years) in which we identified 39 cases. We used IDH1, Ki-67 and Nestin immunomarkers, as well as CDKN2A by FISH. The data were analyzed using SPSS Statistics. The clinical characterization identified only age over 50 years as a risk factor (HR = 3.127). The presence of the tumor residue, as well as the absence of any therapeutic element from the trimodal treatment, were predictive factors of mortality (HR = 1.024, respectively HR = 7.460). Cellular immaturity quantified by Nestin was associated with reduced overall survival (p = 0.007). Increased microvascular density was associated with an increased proliferative index (p = 0.009) as well as alterations of the CDKN2A gene (p < 0.001). CDKN2A deletions and cellular immaturity were associated with an increased percentage of necrosis (p < 0.001, respectively, p = 0.017). The main risk factors involved in the unfavorable prognosis are moderate and increased Nestin immunointensity, as well as the association of increased microvascular density with age over 50 years. Necrosis was not a risk factor.

LRIG3 Suppresses Angiogenesis by Regulating the PI3K/AKT/VEGFA Signaling Pathway in Glioma

High levels of microvessel density (MVD) indicate poor prognosis in patients with malignant glioma. Leucine-rich repeats and immunoglobulin-like domains (LRIG) 3, a potential tumor suppressor, plays an important role in tumor progression and may serve as a biomarker in many human cancers. However, its role and underlying mechanism of action in glioma angiogenesis remain unclear. In the present study, we used loss- and gain-of-function assays to show that LRIG3 significantly suppressed glioma-induced angiogenesis, both in vitro and in vivo. Mechanistically, LRIG3 inhibited activation of the PI3K/AKT signaling pathway, downregulating vascular endothelial growth factor A (VEGFA) in glioma cells, thereby inhibiting angiogenesis. Notably, LRIG3 had a significant negative correlation with VEGFA expression in glioma tissues. Taken together, our results suggest that LRIG3 is a novel regulator of glioma angiogenesis and may be a promising option for developing anti-angiogenic therapy.

Reduced Graphene Oxides Modulate the Expression of Cell Receptors and Voltage-Dependent Ion Channel Genes of Glioblastoma Multiforme

The development of nanotechnology based on graphene and its derivatives has aroused great scientific interest because of their unusual properties. Graphene (GN) and its derivatives, such as reduced graphene oxide (rGO), exhibit antitumor effects on glioblastoma multiforme (GBM) cells in vitro. The antitumor activity of rGO with different contents of oxygen-containing functional groups and GN was compared. Using FTIR (fourier transform infrared) analysis, the content of individual functional groups (GN/exfoliation (ExF), rGO/thermal (Term), rGO/ammonium thiosulphate (ATS), and rGO/ thiourea dioxide (TUD)) was determined. Cell membrane damage, as well as changes in the cell membrane potential, was analyzed. Additionally, the gene expression of voltage-dependent ion channels (clcn3, clcn6, cacna1b, cacna1d, nalcn, kcne4, kcnj10, and kcnb1) and extracellular receptors was determined. A reduction in the potential of the U87 glioma cell membrane was observed after treatment with rGO/ATS and rGO/TUD flakes. Moreover, it was also demonstrated that major changes in the expression of voltage-dependent ion channel genes were observed in clcn3, nalcn, and kcne4 after treatment with rGO/ATS and rGO/TUD flakes. Furthermore, the GN/ExF, rGO/ATS, and rGO/TUD flakes significantly reduced the expression of extracellular receptors (uPar, CD105) in U87 glioblastoma cells. In conclusion, the cytotoxic mechanism of rGO flakes may depend on the presence and types of oxygen-containing functional groups, which are more abundant in rGO compared to GN.

The Interstitial System of the Brain in Health and Disease

The brain interstitial fluid (ISF) and the cerebrospinal fluid (CSF) cushion and support the brain cells. The ISF occupies the brain interstitial system (ISS), whereas the CSF fills the brain ventricles and the subarachnoid space. The brain ISS is an asymmetrical, tortuous, and exceptionally confined space between neural cells and the brain microvasculature. Recently, with a newly developed in vivo measuring technique, a series of discoveries have been made in the brain ISS and the drainage of ISF. The goal of this review is to confer recent advances in our understanding of the brain ISS, including its structure, function, and the various processes mediating or disrupting ISF drainage in physiological and pathological conditions. The brain ISF in the deep brain regions has recently been demonstrated to drain in a compartmentalized ISS instead of a highly connected system, together with the drainage of ISF into the cerebrospinal fluid (CSF) at the surface of the cerebral cortex and the transportation from CSF into cervical lymph nodes. Besides, accumulation of tau in the brain ISS in conditions such as Alzheimer’s disease and its link to the sleep-wake cycle and sleep deprivation, clearance of ISF in a deep sleep via increased CSF flow, novel approaches to remove beta-amyloid from the brain ISS, and obstruction to the ISF drainage in neurological conditions are deliberated. Moreover, the role of ISS in the passage of extracellular vesicles (EVs) released from neural cells and the rapid targeting of therapeutic EVs into neural cells in the entire brain following an intranasal administration, and the promise and limitations of ISS based drug delivery approaches are discussed

Prognostic role of microvessel density in patients with glioma

BACKGROUND

The aim of this study was to systematically evaluate the prognostic role of microvessel density (MVD) in patients with glioma through performing a meta-analysis.

METHODS

Web of Science, EMBASE, PubMed, Cochrane Library, and China National Knowledge Infrastructure were searched for potentially relevant literature. The study characteristics and relevant data were extracted. Hazard ratios (HRs) with 95% confidence intervals (CIs) were pooled to estimate the prognostic role of MVD in patients with glioma.

RESULTS

Nine studies with 536 patients were included. The pooled HR of higher MVD for overall survival (OS) was 1.64 (95% CI, 1.07-2.50) in patients with glioma. Subgroup analyses were also performed. The pooled HRs of higher MVD in studies from East Asia studies examining high-grade gliomas and studies using anti-CD105 antibodies were 1.99 (95% CI, 1.04-3.80), 1.60 (95% CI, 1.09-2.34) and 2.99 (95% CI, 1.50-5.99), respectively. No significant publication bias was found (P = .592), but significant between-study heterogeneity was observed (I = 80.5%, P <.001) in the meta-analysis.

CONCLUSION

Our results suggested that higher MVD was associated with worse OS in patients with glioma. The findings may assist future research on antiangiogenic therapy and help predict prognosis in glioma. However, due to the limited number of studies, more well-designed studies are warranted to further verify our results.

Arterial spin labelling and diffusion-weighted imaging in paediatric brain tumours

BACKGROUND

Diffusion- and perfusion-weighted MRI are valuable tools for measuring the cellular and vascular properties of brain tumours. This has been well studied in adult patients, however, the biological features of childhood brain tumours are unique, and paediatric-focused studies are less common. We aimed to assess the diagnostic utility of apparent diffusion coefficient (ADC) values derived from diffusion-weighted imaging (DWI) and cerebral blood flow (CBF) values derived from arterial spin labelling (ASL) in paediatric brain tumours.

METHODS

We performed a meta-analysis of published studies reporting ADC and ASL-derived CBF values in paediatric brain tumours. Data were combined using a random effects model in order to define typical parameter ranges for different histological tumour subtypes and WHO grades. New data were also acquired in a 'validation cohort' at our institution, in which ADC and CBF values in treatment naïve paediatric brain tumour patients were measured, in order to test the validity of the findings from the literature in an un-seen cohort. ADC and CBF quantification was performed by two radiologists via manual placement of tumour regions of interest (ROIs), in addition to an automated approach to tumour ROI placement.

RESULTS

A total of 14 studies met the inclusion criteria for the meta-analysis, constituting data acquired in 542 paediatric patients. Parameters of interest were based on measurements from ROIs placed within the tumour, including mean and minimum ADC values (ADC_ROI-mean, ADC_ROI-min) and the maximum CBF value normalised to grey matter (nCBF_ROI-max). After combination of the literature data, a number of histological tumour subtype groups showed significant differences in ADC values, which were confirmed, where possible, in our validation cohort of 32 patients. In both the meta-analysis and our cohort, diffuse midline glioma was found to be an outlier among high-grade tumour subtypes, with ADC and CBF values more similar to the low-grade tumours. After grouping patients by WHO grade, significant differences in grade groups were found in ADC_ROI-mean, ADC_ROI-min, and nCBF_ROI-max, in both the meta-analysis and our validation cohort. After excluding diffuse midline glioma, optimum thresholds (derived from ROC analysis) for separating low/high-grade tumours were 0.95 × 10^-3 mm²/s (ADC_ROI-mean), 0.82 × 10^-3 mm²/s (ADC_ROI-min) and 1.45 (nCBF_ROI-max). These thresholds were able to identify low/high-grade tumours with 96%, 83%, and 83% accuracy respectively in our validation cohort, and agreed well with the results from the meta-analysis. Diagnostic power was improved by combining ADC and CBF measurements from the same tumour, after which 100% of tumours in our cohort were correctly classified as either low- or high-grade (excluding diffuse midline glioma).

CONCLUSION

ADC and CBF values are useful for differentiating certain histological subtypes, and separating low- and high-grade paediatric brain tumours. The threshold values presented here are in agreement with previously published studies, as well as a new patient cohort. If ADC and CBF values acquired in the same tumour are combined, the diagnostic accuracy is optimised.

Overexpression of HOXC10 promotes angiogenesis in human glioma via interaction with PRMT5 and upregulation of VEGFA expression

High levels of angiogenesis are associated with poor prognosis in patients with gliomas. However, the molecular mechanisms underlying tumor angiogenesis remain unclear.

Methods: The effect of homeobox C10 (HOXC10) on tube formation, migration, and proliferation of human umbilical vein endothelial cells (HUVECs) and on chicken chorioallantoic membranes (CAMs) was examined. An animal xenograft model was used to examine the effect of HOXC10 on xenograft angiogenesis or the effect of bevacizumab, a monoclonal antibody against vascular endothelial growth factor A (VEGFA), on HOXC10-overexpressing xenografts. A chromatin immunoprecipitation assay was applied to investigate the mechanism in which HOXC10 regulated VEGFA expression.

Results: Overexpressing HOXC10 enhanced the capacity of glioma cells to induce tube formation, migration and proliferation of HUVECs, and neovascularization in CAMs, while silencing HOXC10 had the opposite result. We observed that CD31 staining was significantly increased in tumors formed by HOXC10-overexpressing U251MG cells but reduced in HOXC10-silenced tumors. Mechanistically, HOXC10 could transcriptionally upregulate VEGFA expression by binding to its promoter. Strikingly, treatment with bevacizumab, a monoclonal antibody against VEGFA, significantly inhibited the growth of HOXC10-overexpressing tumors and efficiently impaired angiogenesis. Protein arginine methyltransferase 5 (PRMT5) and WD repeat domain 5 (WDR5), both of which regulate histone post-translational modifications, were required for HOXC10-mediated VEGFA upregulation. Importantly, a significant correlation between HOXC10 levels and VEGFA expression was observed in a cohort of human gliomas.

Conclusions: This study suggests that HOXC10 induces glioma angiogenesis by transcriptionally upregulating VEGFA expression, and may represent a potential target for antiangiogenic therapy in gliomas.

The gain-of-function GLI1 transcription factor TGLI1 enhances expression of VEGF-C and TEM7 to promote glioblastoma angiogenesis

We recently discovered that truncated glioma-associated oncogene homolog 1 (TGLI1) is highly expressed in glioblastoma (GBM) and linked to increased GBM vascularity. The mechanisms underlying TGLI1-mediated angiogenesis are unclear. In this study, we compared TGLI1- with GLI1-expressing GBM xenografts for the expression profile of 84 angiogenesis-associated genes. The results showed that expression of six genes were upregulated and five were down-regulated in TGLI1-carrying tumors compared to those with GLI1. Vascular endothelial growth factor-C (VEGF-C) and tumor endothelial marker 7 (TEM7) were selected for further investigations because of their significant correlations with high vascularity in 135 patient GBMs. TGLI1 bound to both VEGF-C and TEM7 gene promoters. Conditioned medium from TGLI1-expressing GBM cells strongly induced tubule formation of brain microvascular endothelial cells, and the induction was prevented by VEGF-C/TEM7 knockdown. Immunohistochemical analysis of 122 gliomas showed that TGLI1 expression was positively correlated with VEGF-C, TEM7 and microvessel density. Analysis of NCBI Gene Expression Omnibus datasets with 161 malignant gliomas showed an inverse relationship between tumoral VEGF-C, TEM7 or microvessel density and patient survival. Together, our findings support an important role that TGLI1 plays in GBM angiogenesis and identify VEGF-C and TEM7 as novel TGLI1 target genes of importance to GBM vascularity.

Combined local blood-brain barrier opening and systemic methotrexate for the treatment of brain tumors

Despite aggressive therapy, existing treatments offer poor prognosis for glioblastoma multiforme patients, in part due to poor penetration of most drugs across the blood-brain barrier (BBB). We propose a minimal-invasive combined treatment approach consisting of local BBB disruption in the tumor in parallel to systemic drug administration. Local BBB disruption is obtained by convection-enhanced delivery of a novel BBB disruption agent, enabling efficient/targeted delivery of the systemically administered drug by the tumors own vasculature. Various human serum albumin (HSA) analogs were synthesized and screened for BBB disruption efficacy in custom in vitro systems. The candidate analogs were then delivered into naïve rat brains by convection-enhanced delivery and screened for maximal BBB disruption and minimal brain toxicity. These studies found a noncationized/neutralized analog, ethylamine (EA)-HSA, to be the optimal BBB-opening agent. Immunocytochemical studies suggested that BBB disruption by EA-HSA may be explained by alterations in occludin expression. Finally, an efficacy study in rats bearing intracranial gliomas was performed. The rats were treated by convection-enhanced delivery of EA-HSA in parallel to systemic administration of Methotrexate, showing significant antineoplastic effects of the combined approached reflected in suppressed tumor growth and significantly (~x3) prolonged survival.

Combined local blood-brain barrier opening and systemic methotrexate for the treatment of brain tumors

Despite aggressive therapy, existing treatments offer poor prognosis for glioblastoma multiforme patients, in part due to poor penetration of most drugs across the blood-brain barrier (BBB). We propose a minimal-invasive combined treatment approach consisting of local BBB disruption in the tumor in parallel to systemic drug administration. Local BBB disruption is obtained by convection-enhanced delivery of a novel BBB disruption agent, enabling efficient/targeted delivery of the systemically administered drug by the tumors own vasculature. Various human serum albumin (HSA) analogs were synthesized and screened for BBB disruption efficacy in custom in vitro systems. The candidate analogs were then delivered into naïve rat brains by convection-enhanced delivery and screened for maximal BBB disruption and minimal brain toxicity. These studies found a noncationized/neutralized analog, ethylamine (EA)-HSA, to be the optimal BBB-opening agent. Immunocytochemical studies suggested that BBB disruption by EA-HSA may be explained by alterations in occludin expression. Finally, an efficacy study in rats bearing intracranial gliomas was performed. The rats were treated by convection-enhanced delivery of EA-HSA in parallel to systemic administration of Methotrexate, showing significant antineoplastic effects of the combined approached reflected in suppressed tumor growth and significantly (~x3) prolonged survival.

High accuracy of arterial spin labeling perfusion imaging in differentiation of pilomyxoid from pilocytic astrocytoma

INTRODUCTION

Pilomyxoid astrocytoma (PMA) is a relatively new tumor entity which has been added to the 2007 WHO Classification of tumors of the central nervous system. The goal of this study is to utilize arterial spin labeling (ASL) perfusion imaging to differentiate PMA from pilocytic astrocytoma (PA).

METHODS

Pulsed ASL and conventional MRI sequences of patients with PMA and PA in the past 5 years were retrospectively evaluated. Patients with history of radiation or treatment with anti-angiogenic drugs were excluded.

RESULTS

A total of 24 patients (9 PMA, 15 PA) were included. There were statistically significant differences between PMA and PA in mean tumor/gray matter (GM) cerebral blood flow (CBF) ratios (1.3 vs 0.4, p < 0.001) and maximum tumor/GM CBF ratio (2.3 vs 1, p < 0.001). Area under the receiver operating characteristic (ROC) curves for differentiation of PMA from PA was 0.91 using mean tumor CBF, 0.95 using mean tumor/GM CBF ratios, and 0.89 using maximum tumor/GM CBF. Using a threshold value of 0.91, the mean tumor/GM CBF ratio was able to diagnose PMA with 77 % sensitivity, 100 % specificity, and a threshold value of 0.7, provided 88 % sensitivity and 86 % specificity. There was no statistically significant difference between the two tumors in enhancement pattern (p = 0.33), internal architecture (p = 0.15), or apparent diffusion coefficient (ADC) values (p = 0.07).

CONCLUSION

ASL imaging has high accuracy in differentiating PMA from PA. The result of this study may have important applications in prognostication and treatment planning especially in patients with less accessible tumors such as hypothalamic-chiasmatic gliomas.

Dynamic effects of point source electroporation on the rat brain tissue

In spite of aggressive therapy, existing treatments offer poor prognosis for glioblastoma multiforme due to tumor infiltration into the surrounding brain as well as poor blood-brain barrier penetration of most therapeutic agents. In this paper we present a novel approach for a minimally invasive treatment and a non-invasive response assessment methodology consisting of applying intracranial point-source electroporation and assessing treatment effect volumes using magnetic resonance imaging. Using a unique setup of a single intracranial electrode and an external surface electrode we treated rats' brains with various electroporation protocols and applied magnetic resonance imaging to study the dependence of the physiological effects on electroporation treatment parameters. The extent of blood-brain barrier disruption and later volumes of permanent brain tissue damage were found to correlate significantly with the treatment voltages (r(2)=0.99, p<0.001) and the number of treatment pulses (r(2)=0.94, p<0.002). Blood-brain barrier disruption depicted 3.2±0.3 times larger volumes than the final permanent damage volumes (p<0.0001). These results indicate that it may be beneficial to use more than one modality of electroporation when planning a treatment for brain tumors.

Structural and expression differences between the vasculature of pilocytic astrocytomas and glioblastomas

The identification of differences in vascular architecture and utilization of angiogenic pathways is a first step for identifying specific targets for tailored antiangiogenic therapies of brain tumor patients. Here, we compared the proliferating vasculature of 2 glioma subtypes with entirely different biologic behaviors and molecular background at the immunophenotype and gene expression levels. Proliferating vessels in 13 pilocytic astrocytomas and 8 glioblastomas were compared for differences in the composition of the vascular walls using confocal microscopy for markers of endothelial cells and pericytes/mural cells. Endothelial, pericytic, and mural cells had normal-appearing arrangements in the vessels in pilocytic astrocytomas, whereas those in glioblastomas appeared to be more disorganized. In addition, differences in expression of angiogenesis-related genes were sought in the tumor specimens using RNA expression arrays. There were 114 out of 2,894 differentially expressed angiogenesis-related genes between these 2 glioma subtypes indicating differences in the utilization of various pathways. These results point to the need for detailed information on mechanisms of neoangiogenesis in tumor subtypes to facilitate the development of specific antiangiogenic strategies.

Arterial spin-labeled perfusion of pediatric brain tumors

BACKGROUND AND PURPOSE

Pediatric brain tumors have diverse pathologic features, which poses diagnostic challenges. Although perfusion evaluation of adult tumors is well established, hemodynamic properties are not well characterized in children. Our goal was to apply arterial spin-labeling perfusion for various pathologic types of pediatric brain tumors and evaluate the role of arterial spin-labeling in the prediction of tumor grade.

MATERIALS AND METHODS

Arterial spin-labeling perfusion of 54 children (mean age, 7.5 years; 33 boys and 21 girls) with treatment-naive brain tumors was retrospectively evaluated. The 3D pseudocontinuous spin-echo arterial spin-labeling technique was acquired at 3T MR imaging. Maximal relative tumor blood flow was obtained by use of the ROI method and was compared with tumor histologic features and grade.

RESULTS

Tumors consisted of astrocytic (20), embryonal (11), ependymal (3), mixed neuronal-glial (8), choroid plexus (5), craniopharyngioma (4), and other pathologic types (3). The maximal relative tumor blood flow of high-grade tumors (grades III and IV) was significantly higher than that of low-grade tumors (grades I and II) (P < .001). There was a wider relative tumor blood flow range among high-grade tumors (2.14 ± 1.78) compared with low-grade tumors (0.60 ± 0.29) (P < .001). Across the cohort, relative tumor blood flow did not distinguish individual histology; however, among posterior fossa tumors, relative tumor blood flow was significantly higher for medulloblastoma compared with pilocytic astrocytoma (P = .014).

CONCLUSIONS

Characteristic arterial spin-labeling perfusion patterns were seen among diverse pathologic types of brain tumors in children. Arterial spin-labeling perfusion can be used to distinguish high-grade and low-grade tumors.

Angiogenesis in neurological disorders: a review

Angiogenesis, recruitment of new blood vessels, is an essential component of the metastatic pathway. These vessels provide the principal route by which tumor cells exit the primary tumor site and enter the circulation. For many tumors, the vascular density can provide a prognostic indicator of metastatic potential, with the highly vascular primary tumors having a higher incidence of metastasis than poorly vascular tumors. The discovery and characterization of tumor-derived angiogenesis modulators greatly contributed to our understanding of how tumors regulate angiogenesis. However, although angiogenesis appears to be a rate-limiting event in tumor growth and metastatic dissemination, a direct connection between the induction of angiogenesis and the progression to tumor malignancy is less well understood. In this review, we discuss the observations concerning the modulation of angiogenesis and their implications in various neurological disorders, as well as their potential impact on cancer therapy.

Vasculogenic mimicry is a prognostic factor for postoperative survival in patients with glioblastoma

A previous report has confirmed the existence and clinical significance of vasculogenic mimicry (VM) in glioma. However, its conclusions about the negative clinical significance of VM in glioblastoma are based on a small group of patients and, thus, might be unconvincing. The aim of the present study was to reevaluate the clinical significance of VM in glioblastoma. Patients were classified as VM-positive or VM-negative according to CD34 and periodic acid-Schiff staining. The association between VM and the clinical characteristics of the patients was analyzed. Univariate and multivariate analyses were carried out to identify the independent prognostic factors for overall survival using the Cox regression hazard model. Survival times were estimated using the Kaplan-Meier method and compared using the log-rank test. Of all 86 glioblastomas, 23 were found to have VM. The presence of VM in glioblastoma was not associated with gender, age, Karnofsky performance status, hydrocephalus, tumor burden, microvessel density, tumor relapse, or the extent of tumor resection. The univariate and multivariate analyses revealed that VM is an independent prognostic factor for overall survival. The median survival time for patients with VM was 11.17 months compared with 16.10 months for those without VM (P = 0.017). In addition to VM, an age of 65 years or older, a KPS of 60 or less, a large tumor burden are significant prognostic factors for patient survival. Our data suggest that VM might be an independent adverse prognostic factor in newly diagnosed GBM, further prospective studies are needed to answer this question.

Bmi-1 promotes glioma angiogenesis by activating NF-κB signaling

Angiogenesis in glioma is associated with the poor prognosis of the disease and closely correlates with the highly invasive phenotype of glioma cells, which represents the most challenging impediment against the currently glioma treatments. Bmi-1, an onco-protein, has been implicated in the progression of various human cancers, including gliomas, whereas its role in glioma angiogenesis remains unclear. Our current study examined the effects of Bmi-1 on glioma angiogenesis in vitro as well as in vivo. We found that overexpression of Bmi-1 enhanced, whereas knockdown of Bmi-1 diminished, the capability of glioma cells to induce tubule formation and migration of endothelial cells and neovascularization in chicken chorioallantoic membrane. In vivo, Bmi-1 overexpression and knockdown, respectively, promoted and inhibited angiogenesis in orthotopically transplanted human gliomas. Furthermore, NF-κB activity and VEGF-C expression was induced by Bmi-1 overexpression, whereas Bmi-1 knockdown attenuated NF-κB signaling and decreased VEGF-C expression. Additionally suppression of NF-κB activity using a specific chemical inhibitor abrogated the NF-κB activation and the pro-angiogenic activities of glioma cells. Together, our data suggest that Bmi-1 plays an important role in glioma angiogenesis and therefore could represent a potential target for anti-angiogenic therapy against the disease.

Passive immunotherapeutic strategies for the treatment of malignant gliomas

This review provides historical and recent perspectives related to passive immunotherapy for high-grade gliomas. The authors discuss approaches that use lymphokine-activated killer cells, cytotoxic T lymphocytes, and monoclonal antibodies.

Antiangiogenic therapy for glioma

Currently, antiangiogenic agents are routinely used for the treatment of patients with glioma. However, despite advances in pharmacological and surgical therapy, glioma remains an incurable disease. Indeed, the formation of an abnormal tumor vasculature and the invasion of glioma cells along neuronal tracts are proposed to comprise the major factors that are attributed to the therapeutic resistance of these tumors. The development of curative therapeutic modalities for the treatment of glioma requires further investigation of the molecular mechanisms regulating angiogenesis and invasion. In this review, we discuss the molecular characteristics of angiogenesis and invasion in human malignant glioma, we present several available drugs that are used or can potentially be utilized for the inhibition of angiogenesis in glioma, and we focus our attention on the key mediators of the molecular mechanisms underlying the resistance of glioma to antiangiogenic therapy.

CD105 (Endoglin) exerts prognostic effects via its role in the microvascular niche of paediatric high grade glioma

Paediatric high grade glioma (pHGG) (World Health Organisation astrocytoma grades III and IV) remains poor prognosis tumours, with a median survival of only 15 months following diagnosis. Current investigation of anti-angiogenic strategies has focused on adult glioblastoma multiforme (GBM) with phase III trials targeting vascular endothelial growth factor continuing. In this study we investigated whether the degree of vascularity correlated with prognosis in a large cohort of pHGG (n = 150) and whether different vessel markers carried different prognostic value. We found that CD105 (endoglin) had a strongly significant association with poor prognosis on multivariate analysis (p = <0.001). Supervised hierarchical clustering of genome wide gene expression data identified 13 genes associated with differential degrees of vascularity in the cohort. The novel angiogenesis-associated genes identified in this analysis (including MIPOL-1 and ENPP5) were validated by realtime polymerase chain reaction. We also demonstrate that CD105 positive blood vessels associate with CD133 positive tumour cells and that a proportion of CD105 positive vessel cells demonstrates co-positivity for CD133, suggesting that the recently described phenomenon of vasculogenic mimicry occurs in pHGG. Together, the data suggest that targeting angiogenesis, and in particular CD105, is a valid therapeutic strategy for pHGG.

MicroRNA-30e* promotes human glioma cell invasiveness in an orthotopic xenotransplantation model by disrupting the NF-κB/IκBα negative feedback loop

Constitutive activation of NF-κB is a frequent event in human cancers, playing important roles in cancer development and progression. In nontransformed cells, NF-κB activation is tightly controlled by IκBs. IκBs bind NF-κB in the cytoplasm, preventing it from translocating to the nucleus to modulate gene expression. Stimuli that activate NF-κB signaling trigger IκB degradation, enabling nuclear translocation of NF-κB. Among the genes regulated by NF-κB are those encoding the IκBs, providing a negative feedback loop that limits NF-κB activity. How transformed cells override this NF-κB/IκB negative feedback loop remains unclear. Here, we report in human glioma cell lines that microRNA-30e* (miR-30e*) directly targets the IκBα 3ι-UTR and suppresses IκBα expression. Overexpression of miR-30e* in human glioma cell lines led to hyperactivation of NF-κB and enhanced expression of NF-κB-regulated genes, which promoted glioma cell invasiveness in in vitro assays and in an orthotopic xenotransplantation model. These effects of miR-30e* were shown to be clinically relevant, as miR-30e* was found to be upregulated in primary human glioma cells and correlated with malignant progression and poor survival. Hence, miR-30e* provides an epigenetic mechanism that disrupts the NF-κB/IκBα loop and may represent a new therapeutic target and prognostic marker.

Microvessel Density (Chalkley Method) in a Series of 79 Gastrointestinal Stromal Tumors

BACKGROUND

Evaluation of the MVD (modified Chalkley method) in a series of 79 cases of GISTs diagnosed by the Pathology Service at the HCPA (Hospital de Clinicas de Porto Alegre) from January 1993 to December 2009.

METHODS

Seventy nine cases of GISTs were submitted to immunohistochemical analysis for CD31, an endothelial marker, to analyze MVD. Hot spots were identified for each case, and the mean numbers of stained blood vessels collected through Chalkley count, with the use of a 25 point grid, placed onto a scanned image. Images were analysed through an image analysis system. We used a cutoff of six vessels.

RESULTS

Our series was composed of 42 males and 37 females and presented an average age of 58.9 years. GISTs were predominately located in the stomach (45.6%) followed by the small intestine (38.0%). Sixty seven GISTs (84.8%) showed an average of less than six vessels stained by CD31 (MVD) and 12 (15.2%) GISTs an average of more than six vessels. A statistically significant difference was observed between survival rate of patients having GISTs with MVD of ≤ 6 vessels (mean = 2.4, CI 95%: 1.67 - 3.17) and patients having GISTs with MVD of ≥ 6 vessels (mean = 2.4, CI 95%: 1.67 - 3.17), P = 0.001. No association for MVD was observed related to sex, age, histological type, risk category, location and metastasis.

CONCLUSIONS

Seventy nine cases of GISTs diagnosed at a single center in South Brazil were studied for MVD (Chalkley method). There was a statistically significant difference between MVD and the survival rate for these patients. The use of Chalkley method in GISTs may be helpful to evaluate clinical outcome.

Inhibitors of Glioma Growth that Reveal the Tumour to the Immune System

Treated glioblastoma patients survive from 6 to 14 months. In the first part of this review, we describe glioma origins, cancer stem cells and the genomic alterations that generate dysregulated cell division, with enhanced proliferation and diverse response to radiation and chemotherapy. We review the pathways that mediate tumour cell proliferation, neo-angiogenesis, tumor cell invasion, as well as necrotic and apoptotic cell death. Then, we examine the ability of gliomas to evade and suppress the host immune system, exhibited at the levels of antigen recognition and immune activation, limiting the effective signaling between glioma and host immune cells.The second part of the review presents current therapies and their drawbacks. This is followed by a summary of the work of our laboratory during the past 20 years, on oligosaccharide and glycosphingolipid inhibitors of astroblast and astrocytoma division. Neurostatins, the O-acetylated forms of gangliosides GD1b and GT1b naturally present in mammalian brain, are cytostatic for normal astroblasts, but cytotoxic for rat C6 glioma cells and human astrocytoma grades III and IV, with ID50 values ranging from 200 to 450 nM. The inhibitors do not affect neurons or fibroblasts up to concentrations of 4 μM or higher.At least four different neurostatin-activated, cell-mediated antitumoral processes, lead to tumor destruction: (i) inhibition of tumor neovascularization; (ii) activation of microglia; (iii) activation of natural killer (NK) cells; (iv) activation of cytotoxic lymphocytes (CTL). The enhanced antigenicity of neurostatin-treated glioma cells, could be related to their increased expression of connexin 43. Because neurostatins and their analogues show specific activity and no toxicity for normal cells, a clinical trial would be the logical next step.

Clinical significance of vasculogenic mimicry in human gliomas

Vasculogenic mimicry (VM) is known as non-endothelial tumor cell-lined microvascular channels in aggressive tumors. We have previously found the presence of VM in high-grade gliomas. In this study, we aimed to identify VM patterns in gliomas and to explore their clinical significance. Tumor samples as well as their detailed clinical/prognostic data were collected from 101 patients. Vasculogenic mimicry in the glioma samples was determined by dual staining for endothelial marker CD34 and periodic acid–Schiff (PAS). Tumor samples were also immunohistochemically stained for Ki-67, VEGF, COX-2 and MMP-9. The association between VM and the clinical characteristics of the patients were analyzed. A Kaplan–Meier survival analysis and log-rank tests were performed to compare survival times of the patients. Vasculogenic mimicry was present in 13 out of 101 samples. The higher grade gliomas had a higher incidence of VM than that of lower grade gliomas (P = 0.006). Vasculogenic mimicry channels were associated with the expression of COX-2 and MMP-9 (P < 0.05). While there was no association between the existence of VM and the sex, age and preoperative epilepsy of the patients, or expression of Ki-67 and VEGF. However, patients with VM-positive gliomas survived a shorter period of time than those with VM negative gliomas (P = 0.027). Interestingly, in high-grade gliomas, the level of microvascular density was lower in VM positive tumors than those VM negative tumors (P = 0.039). Our results suggest that VM channels in gliomas correlate with increasing malignancy and higher aggressiveness, and may provide a complementation to the tumor’s blood supply, especially in less vascularized regions, which may aid in the identification of glioma patients with a poorer prognosis.

Prospective evaluation of angiogenic, hypoxic and EGFR-related biomarkers in recurrent glioblastoma multiforme treated with cetuximab, bevacizumab and irinotecan

Several recent studies have demonstrated a beneficial effect of anti-angiogenic treatment with the vascular endothelial growth factor-neutralizing antibody bevacizumab in recurrent high-grade glioma. In the current study, immunohistochemical evaluation of biomarkers involved in angiogenesis, hypoxia and mediators of the epidermal growth factor receptor (EGFR) pathway were investigated. Tumor tissue was obtained from a previous phase II study, treating recurrent primary glioblastoma multiforme (GBM) patients with the EGFR inhibitor cetuximab in combination with bevacizumab and irinotecan. Of the 37 patients with available tumor tissue, 29 were evaluable for response. We concurrently performed immunohistochemical stainings on tumor tissue from 21 GBM patients treated with bevacizumab and irinotecan. We found a tendency of correlation between the hypoxia-related markers, indicating that they share the same regulatory mechanisms. None of the EGFR-related biomarkers showed any significant correlations with each other. None of the biomarkers tested alone or in combination could identify a patient population likely to benefit from bevacizumab and irinotecan, with or without the addition of cetuximab. There is still an urgent need for one or more reliable and reproducible biomarkers able to predict the efficacy of anti-angiogenic therapy.

Passive antibody-mediated immunotherapy for the treatment of malignant gliomas

Despite advances in understanding the molecular mechanisms of brain cancer, the outcome of patients with malignant gliomas treated according to the current standard of care remains poor. Novel therapies are needed, and immunotherapy has emerged with great promise. The diffuse infiltration of malignant gliomas is a major challenge to effective treatment; immunotherapy has the advantage of accessing the entire brain with specificity for tumor cells. Therapeutic immune approaches include cytokine therapy, passive immunotherapy, and active immunotherapy. Cytokine therapy involves the administration of immunomodulatory cytokines to activate the immune system. Active immunotherapy is the generation or augmentation of an immune response, typically by vaccination against tumor antigens. Passive immunotherapy connotes either adoptive therapy, in which tumor-specific immune cells are expanded ex vivo and reintroduced into the patient, or passive antibody-mediated therapy. In this article, the authors discuss the preclinical and clinical studies that have used passive antibody-mediated immunotherapy, otherwise known as serotherapy, for the treatment of malignant gliomas.

The functional role of Notch signaling in human gliomas

Gliomas are among the most devastating adult tumors for which there is currently no cure. The tumors are derived from brain glial tissue and comprise several diverse tumor forms and grades. Recent reports highlight the importance of cancer-initiating cells in the malignancy of gliomas. These cells have been referred to as brain cancer stem cells (bCSC), as they share similarities to normal neural stem cells in the brain. The Notch signaling pathway is involved in cell fate decisions throughout normal development and in stem cell proliferation and maintenance. The role of Notch in cancer is now firmly established, and recent data implicate a role for Notch signaling also in gliomas and bCSC. In this review, we explore the role of the Notch signaling pathway in gliomas with emphasis on its role in normal brain development and its interplay with pathways and processes that are characteristic of malignant gliomas.

Brain angiogenesis in developmental and pathological processes: mechanism and therapeutic intervention in brain tumors

Formation of new blood vessels is required for the growth and metastasis of all solid tumors. New blood vessels are established in tumors mainly through angiogenesis. Brain tumors in particular are highly angiogenic. Therefore, interventions designed to prevent angiogenesis may be effective at controlling brain tumors. Indeed, many recent findings from preclinical and clinical studies of antiangiogenic therapy for brain tumors have shown that it is a promising approach to managing this deadly disease, especially when combined with other cytotoxic treatments. In this minireview, we summarize the basic characteristics of brain tumor angiogenesis and the role of known angiogenic factors in regulating this angiogenesis, which may be targets of antiangiogenic therapy. We also discuss the current status of antiangiogenic therapy for brain tumors, the suggested mechanisms of this therapy and the limitations of this strategy.

Malignant astrocytic glioma: genetics, biology, and paths to treatment

Malignant astrocytic gliomas such as glioblastoma are the most common and lethal intracranial tumors. These cancers exhibit a relentless malignant progression characterized by widespread invasion throughout the brain, resistance to traditional and newer targeted therapeutic approaches, destruction of normal brain tissue, and certain death. The recent confluence of advances in stem cell biology, cell signaling, genome and computational science and genetic model systems have revolutionized our understanding of the mechanisms underlying the genetics, biology and clinical behavior of glioblastoma. This progress is fueling new opportunities for understanding the fundamental basis for development of this devastating disease and also novel therapies that, for the first time, portend meaningful clinical responses.